Motorbike conversion speculation

Technical discussion on converting internal combustion to electric
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89rx0ff
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Motorbike conversion speculation

Post by 89rx0ff » Fri, 03 Sep 2010, 02:49

Hi Guys/Gals,

I am quite new to the whole EV conversion process but still planning on going ahead with my conversion.

My donor bike is a 91 Kawasaki 750 roadbike.

I am looking at using the following,

4x 12v 50ah SLA deep cycle batteries
Mars ME0708 48V DC motor
Alltrax 48V 400A AXE4844 DC Motor Controller

using the emoto spreadsheet from this website i could only get a estimate on a 72v system.

So i am wondering what you guys think about my 48V system (as minimal as the information that i am giving is)

all i want to achieve is a distance of 45km (approx)
and a 100km speed (average)

now is my top speed more realitive to my gear ratio than my controller?
Would my batterys have the ability to give me the distance that i want to achieve?

i just want to get opinions of the experienced people before i start my project.......

Also i am having difficulty finding any information in regards to having a road registered electric bike... are they legal? where can i get the information on conversions?

do i just apply for a vehicle modification through the state roads authority?

thanks in advance
george

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Electrocycle
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Motorbike conversion speculation

Post by Electrocycle » Fri, 03 Sep 2010, 04:40

the issue with bikes is that they have a lot of aerodynamic drag over about 80km/h, so doing 100km/h takes a lot of power.

Top speed will be limited by the gearing, and by the battery and controller power available.
With that motor you wouldn't be able to maintain 100km/h for long without cooking it, but it will give decent performance at lower speeds.

This is the bike I converted a while back: EPX on EV Album

With a 36v 36Ah battery pack I got around 15km range and a top speed of 70km/h.

I think you need to run the motor at a higher voltage to get a wider usable speed range from it. If you stick to the rated 48v you'll need to gear it too tall to acheive your top speed - so the acceleration and efficiency will suffer down low.
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Thalass
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Motorbike conversion speculation

Post by Thalass » Tue, 14 Sep 2010, 04:44

You should be able to change the voltage on that spreadsheet. If it's the one i've been using. You enter the battery voltage per battery, and the number of them, (and the ah of each one) and it works from those numbers.


I have to say i donlt like your chances, though it's not as bad as i may have thought. My spreadsheet says ~32km range. I do think it's somewhat optimistic - it tells me my bike will go over 100km! (assuming i can fit 100ah cells in there)


If you're willing to spend a few thousand instead of a few hundred on lithium cells, you could get your 100km range, and if you go for at least 72 volts you might get your 100km/h. It depends on other factors, of course, like aerodynamics. A 750cc bike will also have an easier time fitting all those cells. I suspect i'll have to suck it up and go for 60ah cells in my 250.

I really don't think you'll be satisfied with lead and 48v. Have a look on evalbum at the bikes on there. Most are lead, and many are lucky to get 20km or so.
I'll drive an electric vehicle one day.

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Richo
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Motorbike conversion speculation

Post by Richo » Wed, 29 Sep 2010, 05:33

4 x 12V 50Ah SLA might be able to put out 13-14kW peak (briefly)
So I hope you were not expecting for 250cc performance (20-30kW).
As others have said you will need more voltage to get to 100km/hr.
A small series DC motor would be better suited.

Still it would make a good urban runner with around 20km range.

We need more motorbike conversions.
So the short answer is NO but the long answer is YES.
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Richo
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Motorbike conversion speculation

Post by Richo » Wed, 29 Sep 2010, 05:49

89rx0ff wrote:now is my top speed more realitive to my gear ratio than my controller?

Your top speed is a combination of your complete system.
To move your bike at 100km/hr you will need a certain amount of power.
The batteries, controller and motor must be able to provide this power.
If one is less then this becomes the limit.
Also with DC the gearing will determine the RPM of the motor which will decide your pack voltage from the back EMF.
89rx0ff wrote: Would my batterys have the ability to give me the distance that i want to achieve?
No. well yes but not at 100km/hr.
You use much less power at 50km/hr so might make 40km at this speed.
89rx0ff wrote: Also i am having difficulty finding any information in regards to having a road registered electric bike... are they legal? where can i get the information on conversions?

NCOP14 still applies to motorbike conversions.
As others point out they are legal and already exist.
89rx0ff wrote: do i just apply for a vehicle modification through the state roads authority?

It may be different in your state but that is what I would do in WA.
Then they can respond in writing if there are any particular concerns.
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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Motorbike conversion speculation

Post by antiscab » Thu, 30 Sep 2010, 00:11

Hi George,
89rx0ff wrote:

4x 12v 50ah SLA deep cycle batteries
Mars ME0708 48V DC motor
Alltrax 48V 400A AXE4844 DC Motor Controller

*snip*

all i want to achieve is a distance of 45km (approx)
and a 100km speed (average)


100kmh takes around 7kw continuous.
45km means your battery needs a usable capacity of 3.15kwh

if this is your daily commute, that usable capacity should be 4.5kwh to accommodate lifetime capacity loss and hard riding days (big head winds).

4 x 12v 50Ah deep cycle batteries will give you around 1.2kwh.

to get 45km @ 100kmh, you really will need lithium.

I would highly recommend going for at least 72v.
at 100kmh, that will be 100A continuous.

that would be 24 cells, and at least 80Ah.

the Major cell manufacturers make 90Ah cells as the closest cell size.

as has been alluded to earlier, going slower makes the requirements a bit easier.

Matt

Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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Motorbike conversion speculation

Post by Electrocycle » Thu, 30 Sep 2010, 02:29

fitting 24 90Ah cells in a bike is also a tricky job!
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Motorbike conversion speculation

Post by antiscab » Thu, 30 Sep 2010, 03:00

it sure is, especially if you want easy access to the cells aswell.

I was once considering putting that much in a suzuki across.

putting the pack in two layers helps with fitting it in, its just a pain if you ever need to get to the bottom cells.
I've found you don't need access to the cells all that often.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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Post by Electrocycle » Thu, 30 Sep 2010, 03:12

yeah my VT250 has 20 TS 60Ah cells, which are in two layers.

Even then I wouldn't be able to fit more than a couple more without starting to have them spread out all over the bike.

The pack is around 50kg, which is pretty close to the weight of an average 250cc bike engine - so you're not left with a whole lot of weight for the motor and controller.
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Richo
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Motorbike conversion speculation

Post by Richo » Thu, 30 Sep 2010, 04:41

I will be struggling to fit in 90 x 10Ah headway cells into the frame of my bike.
But they will be arranged across so the ends point out each side of the bike.
So it will make easy access to the wiring and BMS modules.
My pack should be good for about 25kW peak which is similar to a 250cc
I guess if I was keen on more range I would have gone Lipo poly packs to squeeze them all in.

If the mars DC motor can't do the job which series DC motor could do 7kW cont with something like 20-30kW peak?
So the short answer is NO but the long answer is YES.
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antiscab
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Motorbike conversion speculation

Post by antiscab » Thu, 30 Sep 2010, 05:10

An ADC k91 is 7.3kw cont, 23kw peak @ 96v.
weighs 25kg though.
still need 30 cells though. (60Ah should be enough)

George - do you know how much the engine and such weighs on a kawasaki 750?

there is the enertrac 10kw hub motor, but now were getting expensive (though heading towards 600 performance).

also, how much space do you have in a 750 frame?

the advantage of a bigger bike is you can fit more stuff into it :D

these questions are easier to answer if you already own the bike.
do you already own a 91 750?
or are you scoping out the suitability of the various models?
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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Richo
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Motorbike conversion speculation

Post by Richo » Thu, 30 Sep 2010, 21:02

I guess in comparison a 2.2kW ACIM is about 20kg with similar ratings.
Difference is you would need around 330Vdc.
So 4.5kWh at 330V dc is 103 x 3.2V 14Ah LiFePO4. (EVPST cells perhaps)
or 90 x 3.7V Li-po 14Ah (3 x 5Ah in parallel hobby king)
or 28 x 12V 14Ah SLA (usu 12V 12Ah)
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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Post by carnut1100 » Fri, 04 Mar 2011, 04:53

I think using abigger bike could have advantages in that it is designed for a bigger weight and can hold more batteries...
One thing though, if you use a non-LAMS approved bike for the donor, but the power is naturally inside the LAMS rules of 150kW/tonne and it does not go over a ICE cc limit, can you then get the bike registered as a LAMS approved bike?

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Post by Electrocycle » Fri, 04 Mar 2011, 12:39

LAMS is actually a list of approved bikes, not just a power to weight ratio thing, so it may be difficult to get anything larger approved.
I think it may come down to who you talk to when you register it.

Hopefully it's possible - but then part of the LAMS requirements are to do with the weight, to make it easier to handle for inexperienced riders, so having a large heavy bike might not be ideal even if it fits in the power to weight ratio limit.
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Post by carnut1100 » Sun, 06 Mar 2011, 23:42

I've been looking into this talking to various people in Tasmanian transport and registry departments.
They basically said that getting anything added to LAMS is nigh-on impossible.
However, if one started with a LAMS bike and proved to Transport that the modifications did not take it out of the power to weight parameters of LAMS then the modification plate could be marked to that effect and if so then the bike would still be LAMS approved for the purposes of registration. If the mod plate does not specifically state however that the bike remains within the parameters of LAMS then the LAMS status of the bike would be automatically nullified.

The only possible way to get a conversion based on a bigger bike approved would look to be registering it as a brand new individually constructed vehicle and applying for LAMS approval under that. Loads more hoops to jump through basically.

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